At macro distances, the movement is primarily forward and back - IS doesn't help in that case. Faster shutter speed [even with higher ISO] or flash is a better answer.

Really? At macro distances and hand-held, if I turn off IS and look throught the VF, I see all kinds of shifting including horizontala and rotational, not just back and forth. IS certainly is not AS useful at macro distances but is still useful for me for hand-held macro shots, making the difference between getting the shot or not on my 100L..

I am no macro expert, but I find the IS easier to use than the Sigma 105 2.8 Macro I had before. That being said I am often trying to hand hold macro shots which is really not the way to do it. You pretty much have to use a tripod to get acceptable results, so no real benefit in an IS lens.

Overall, the Canon 100 L is a fantastic lens. It takes excellent tight portraits and the IS helps here.

IS is useful when taking pics handheld. The effectiveness of IS decreases the closer you get to 1:1, but it still helps. Most pics taken with macros are not 1:1 anyway. Serious macro users will use f/11 or smaller and use tripods/rails/flashes and focus stack. IS doesn't do you any good for using a lens this way, but for everyone else who wants to have macro capability and do most of it handheld, IS is a winner. IS also makes it more user-friendly as a portrait/general use lens.

My advice is to try the 100L macro. It is excellent. The IS works very well - look through live view with IS on and off and the difference immediately becomes obvious. You have 9 apperture baldes and weather sealing to boot.I've seen this thread numerous times asking is the 100L worth the extra money. I've not yet seen a reply by anyone that owns this lens saying they regret their purchase. If you can afford it, buy it!

i have a tamron 90mm f2,8 macro and im very happy with it... except one thing.

sometime i don´t have a tripod with me or in some locations tripods are not allowed.and then camera shake is an issue when i shoot handheld macros of flowers etc.

i would like to buy the EF 100 mm macro with IS. but i remember reading some comments that IS is pretty useless for macro.

did they mean because you should shoot on a tripod anyway ... or why is it that i read this comment quite often?

I sold my Tamron 90mm f/2.8 macro & Sigma 150mm f/2.8 macro and bought the EF 100mm f/2.8 L IS macro lens ... i100 L IS is far more sharper at f/2.8 than the Tamron or the Sigma ... the IS works really well and is a great help ... you will not regret buying the 100 L IS.Regarding tripod, yes absolutely! no amount of Image Stabilization will work as well as a tripod ... but a tripod is not always convenient to carry around ... most of my macro shots happen at random places, like restaurants (most good restaurant have beautiful and interesting small objects), shopping malls etc and carrying a tripod to those places is not very convenient, so the IS helps a lot ... I tried photographing butterflies and dragonflies with a tripod, but by the time I could set up my tripod it was too late ... Image Stabilization really helps in such situations.

If you wanted a dedicated Macro lens that you only use on a tripod, then I suppose not. But, I shoot a lot more at "near macro" than I do true macro and I like to wander around outside getting close to things.

Shooting macro in the field is very difficult. People who don't do it regularly don't always realize just how tricky it can be. It's a real challenge to get the tripod exactly where you want it to accurately frame the image in the the way you envision it.

Remember, everything is magnified. The light can be perfect in one spot for 30 seconds and then a tiny shift and it's gone. An insect on a leaf will move out of the frame. The slightest breeze and your perfectly framed shot suddenly has shifted. An image looks perfect when you are kneeling on the ground, but shift your back slightly, and you lose it.

I can't count the number of times when I've started out using a tripod and just gave up and switched over to hand holding, because I couldn't possibly position the tripod precisely where I wanted it or do it quickly enough so as not to lose the light or the framing.

Oftentimes I find myself framing an image, pre-setting the focus and then physically moving in closer or further away as I try to get the most interesting part of the subject in focus. That's pretty much impossible to do with a tripod, and the IS definitely helps.

Plus, it's a great portrait lens and modest telephoto. Both things that make the IS very valuable.

Get the Canon 100mm 2.8 IS USM. B+H is selling it with their 2% savings sale for $899.00. I haven't used it on my tripod yet. I am very happy with this lens. I paid more when I bought 3 years ago but now seems to be a good time to buy.